DESCRIPTION: Dr. Russo has developed an in vitro system for the transformation of human breast epithelial cells (HBEC) that recapitulates different stages of tumor initiation and progression, culminating in the expression of malignancy. HBEC were initially isolated from a patient with fibrocystic disease, and samples of this primary isolate are still available. From the primary HBEC, the immortalized MCF10A and F lines arose spontaneously. The MCF10F cells were treated with benzo(a)pyrene, and the resultant clones express in a progressive fashion all the phenotypes indicative of neoplastic transformation, from increased survival in agar, formation of colonies in agar methocel, invasiveness in matrigel, to tumorigenicity in SCID mice. This model system will be used to investigate whether loss of heterozygosity at various chromosomal loci plays a functional role in the expression of the tumorigenic phenotype. The following specific aims will be pursued. Aim 1. To determine whether allelic losses occur in tumors induced in SCID mice by transplant of transformed HBEC. Allelic losses in chromosomes 1,2,3,6,7,11,13,16,17,18 and 22 will be evaluated. Aim 2. To determine what alleles are lost during the sequential steps of cell transformation. This aim will focus on which of the alleles found to be lost in tumors, are associated with the expression of specific stages of neoplastic initiation or progression in the preneoplastic cell lines. Aim 3. To determine whether allelic losses which have been identified to be relevant in the expression of the transformation and tumorigenic phenotypes have a functional role as tumor suppressor genes. For this purpose, chromosomal transfer techniques will be used to revert or to enhance the tumorigenic and transformation phenotypes. The hypothesis to be tested is that tumor suppressor genes detected as loss of genetic material (LOH) play a functional role in initiation and progression of breast cancer. The goal is to clarify the role of LOH in each stage of breast cancer progression - ductal hyperplasia, atypical ductal hyperplasia, carcinoma in situ, invasive and metastatic adenocarcinoma. Since all of the stages are not present in a single patient or in a sequential manner, Dr. Russo has developed an in vitro model for transformation of human breast epithelial cells (HBEC) that recapitulates the different stages of tumor initiation and progression. This correlates with similar loss observed in primary breast cancer. Thus this in vitro model mimics the in vivo situation.